Updating BlueZ on Raspberry Pi (5.43 to 5.48)

This post shows how to update BlueZ from 5.43 (the default version comes with Raspbian Stretch November 2017 version) to 5.48 (the latest as of 2/14/2018) on Raspberry Pi.
According to the release notes [1], many issues (especially GATT related issues) have been fixed and also, Advertising Manager API, which was previously marked as experimental, is now stable in 5.48.